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THE TONGA PLANT {EPIPREMNUM MIRABILE, Schott). 

 By N. E. Brown, A.L.S. 



In the 'Gardener's Chronicle,' 1882, xvii., p. 180, Ipubhshed a 

 general account of the Tonga Plant, promising elsewhere to publish 

 the botanical details of its very involved synonymy ; this promise 

 I now keep, but as there are probably many readers of the 

 * Journal of Botany' who may not have the ' Gardener's Chronicle,' 

 I have thought it would be useful to embody the account therein 

 published. 



Tonga is a vegetable drug, and the material from which it 

 is prepared is stated to consist of a mixture of bark and fibrous 

 matter, the botanical origin of which was for some time unknown. 

 Some months back, however, an interesting account of the plants 

 producing this drug was published in the ' Gardener's Chronicle,' 

 xvi., p. 1107, where it is stated, upon the authority of Baron von 

 Mueller, that Tonga is a product of Premna taitensis and Rhaphi- 

 dophora vitiensis. This account was communicated by Mrs. Glen- 

 dinning, and with it she also sent specimens of the Tonga plants, 

 which were kindl}' presented by the editor of the ' Gardener's 

 Chronicle ' to the Kew Museum. In the ' Eeport of the Eoyal 

 Gardens, Kew,' for 1880, published towards the end of last year, 

 it is stated that Mr. E. M. Holmes, curator of the Museum of the 

 Pharmaceutical Society, also arrived at the conclusion that Piha- 

 phidophora vitiensis was probably one of the plants from which 

 Tonga is in part derived, and that Mr. C. W. Hansen, w^hilst in 

 Fiji, was enabled to confirm this determination as correct, and to 

 add that he (Mr. Hansen) believed the other plant that enters into 

 the composition of Tonga to be Premna taitensis. 



We thus have evidence from two independent sources that the 

 di'ug Tonga is a product partly derived from Premna taitensis and 

 partly fi'om Rhaphidophora vitiensis ; and now that we know this, 

 it is interesting to know that one of these plants, and that most 

 probably the one to which the reputed medicinal vu'tues of Tonga 

 are due, has been in cultivation in this country during the past 

 four or five years. For upon seeing the specimens of the Tonga 

 plants sent by Mrs. Glendinning, I immediately recognised the 

 Aroid as being identical with a plant cultivated by Mr. W. Bull, of 

 Chelsea, of which I had dried specimens for the Kew Herbarium. 



As this plant is involved in great confusion botanically, I think 

 it better that I should here give full details concerning it. 



Mr. Bull's plant was introduced from the Fiji Islands by way 

 of the Botanic Garden at Sydney, New South Wales, and it has 

 behaved exactly as described in Mrs. Glendinning' s note (though I 

 may here observe that this mode of gi'adual development and 

 change of form in the leaf, as described below, is by no means rare 

 in the groups of Aroids to which it belongs). When first received 

 the stem was very slender, about one-eighth of an inch thick, and 

 the leaves were very small and quite entire ; but upon being 

 allowed to creep up a wall or some other sui^port, the stem rapidly 



